Oil pump

ABSTRACT

A guide slot having an elongated-hole shape is formed in a capacity adjustment member, so that displacement of the capacity adjustment member is regulated, by a guide pin inserted into the guide slot, to a longitudinal direction of the guide slot. Two spaces separated by the guide pin into one side and the other side in the longitudinal direction of the guide slot are formed inside the guide slot, and a communicating passage is provided so as to communicate the spaces with each other.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2014-119363 filed onJun. 10, 2014 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a variable-capacity oil pump.

2. Description of Related Art

Japanese Patent Application Publication No. 2013-100737 (JP 2013-100737A) describes an oil pump constituted by an internal gear pump configuredto discharge, from a discharge port, oil taken in from an inlet port byrotation of an inner rotor (a drive rotor) and an outer rotor (a drivenrotor) meshing with each other.

The oil pump includes an adjustment ring (a capacity adjustment member)so as to rotatably hold the outer rotor from its outer periphery in ahousing. The adjustment ring is displaced by receiving a hydraulicpressure introduced into a pressurizing space in the housing. Hereby,relative positions of the inner rotor and the outer rotor to the inletport and the discharge port are changed. Due to the change of thepositions of the inner rotor and the outer rotor, a discharge amount (aso-called displacement volume) per one rotation of an input shaft, thatis, a pump capacity, is changed.

In JP 2013-100737 A, the adjustment ring is provided with an elongatedhole (a guide slot having an elongated-hole-shaped section). Thedisplacement of the adjustment ring is regulated by a guide pin insertedinto the elongated hole. That is, when the adjustment ring is displacedby the hydraulic pressure in the pressurizing space as described above,a direction of the displacement is regulated to a direction where theelongated hole extends.

When the adjustment ring is displaced in the direction where theelongated hole extends, the guide pin is relatively displaced inside theelongated hole in a longitudinal direction of the elongated hole. Thatis, an inner part of the elongated hole is divided by the guide pin intoone side and the other side in the longitudinal direction. When theadjustment ring is displaced, the guide pin is displaced relative to theelongated hole in the longitudinal direction of the elongated hole.

The inner part of the elongated hole thus divided by the guide pin isdivided into two spaces on the one side and the other side in thelongitudinal direction of the elongated hole. When the guide pin isrelatively displaced as described above, oil flows through a gap betweenan outer peripheral surface of the guide pin and an inner peripheralsurface of the elongated hole that makes sliding contact with the outerperipheral surface of the guide pin, so as to go back and forth betweenthe two spaces.

SUMMARY OF THE INVENTION

In order to regulate the direction of the displacement of the adjustmentring with accuracy, it is necessary for the gap between the outerperipheral surface (a guide surface) of the guide pin and the innerperipheral surface (a guided surface) of the guide slot that slides tobe narrowed sufficiently. Because of this, a flow resistance of the oilin the narrow gap increases, which may become a resistance to thedisplacement of the adjustment ring. Particularly, when a viscosity ofthe oil is high like a case where a temperature is low, the resistanceincreases, so that the displacement of the adjustment ring becomes slow.Therefore, in this case, response of a control on a pump capacity maydecrease.

The present invention provides a variable-capacity oil pump thatimproves response of control.

One aspect of the present invention relates to an oil pump including aninput shaft, an inlet port, a discharge port, a capacity-variablemechanism and a housing. The capacity-variable mechanism is configuredto change a discharge amount per one rotation of the input shaft. Thecapacity-variable mechanism includes a capacity adjustment member. Thecapacity adjustment member has a guide slot having an elongated-holeshape. The guide slot includes a guided surface provided on an innerperiphery of the guide slot. The housing includes a guide pin. The guidepin is inserted into the guide slot. The guide pin includes a guidesurface provided on an outer periphery of the guide pin. The guide pinis configured to regulate displacement of the capacity adjustment memberto a longitudinal direction of the guide slot. The guide pin isconfigured to separate the guide slot into a first space and a secondspace in the longitudinal direction. The guide surface of the guide pinmakes sliding contact with the guided surface of the guide slot. Oilflows between the first space and the second space via a gap between theguide surface and the guided surface. At least one of the guide pin andthe capacity adjustment member is provided with a communicating passage,and the communicating passage is configured to communicate the firstspace with the second space.

According to the above configuration, the oil flows through a gapbetween an outer peripheral surface (the guide surface) of the guide pinand that inner peripheral surface (the guided surface) of the guide slotwhich makes sliding contact with the outer peripheral surface of theguide pin, so as that the oil goes back and forth between two spaces inthe guide slot, and the oil also flows through the communicating passagethat communicates the two spaces with each other. Thus, the oil flowsthrough the communicating passage as well as the gap between the guidepin and the guide slot. Hereby, a flow resistance of the oil is reduced,so that the capacity adjustment member is displaced fast. As a result,improvement of response of a control on a pump capacity is achieved.

In the above oil pump, a sectional area of the communicating passage maybe larger than a sectional area of the gap between the guide surface andthe guided surface. According to the above configuration, an effect toreduce the flow resistance of the oil going back and forth between twospaces in the guide slot is high.

In the above oil pump, the guide pin may include a first sectional areapart and a second sectional area part along an axial direction of theguide pin. The first sectional area part may have a sectional areasmaller than that of the second sectional area part. The guide pin mayinclude a recess provided on an outer peripheral surface of the guidepin in the first sectional area part. The recess may constitute thecommunicating passage. According to the above configuration, thecommunicating passage can be easily configured with a simple structureto change an outer shape of the guide pin.

In this case, the recess on the outer periphery of the guide pin doesnot function as the guide surface. In view of this, in the above oilpump, the first sectional area part may be provided at an axiallyintermediate part of the guide pin. According to the aboveconfiguration, outer peripheral surfaces of both axial ends of the guidepin function as the guide surface. This accordingly achievesstabilization of a guiding function of the guide pin.

In the above oil pump, the first sectional area part of the guide pinmay include a tapered part having a sectional area that graduallyincreases toward the second sectional area part. In the aboveconfiguration, a tip end of the guide pin may be provided as a smallsectional area part (the first sectional area part) having a sectionalarea smaller than that of the other part of the guide pin. With such aconfiguration, most part of the outer peripheral surface of the guidepin except the tip end thereof exhibits the guiding function, so thatthe guiding function is easy to be secured. Besides, since the tip endof the guide pin has a tapered shape, demolding can be easily performedin a case where the guide pin is formed integrally with a pump housingat the time of casting the pump housing.

In the above oil pump, the communicating passage may penetrate throughthe guide pin, and the communicating passage may be configured tocommunicate the first space with the second space. In the above oilpump, an inner peripheral surface of the guide slot may have a grooveextending in a longitudinal direction of the guide slot, and the groovemay constitute the communicating passage. In the above oil pump, thecommunicating passage may be provided inside the capacity adjustmentmember, and both ends of the communicating passage may be opened on aninner peripheral surface of the guide slot.

In the above oil pump, the housing may include a low hydraulic chamber,and the guide slot may communicate with the inlet port via the lowhydraulic chamber. In this case, a negative pressure on an intake sideof the oil pump is applied inside the guide slot. In this case, at thetime when the guide pin is relatively displaced in the guide slot asdescribed above, the negative pressure increases (a pressure decreases)in a space of which a volume increases along with the displacement,which may cause cavitation.

In contrast, according to the above configuration, at the time when theguide pin is relatively displaced in the guide slot as described above,the flow resistance of the oil going back and forth between two spacesis reduced. This makes it possible to restrain an increase in thenegative pressure (a decrease in the pressure) in the space of which thevolume increases. Accordingly, an effect to restrain an occurrence ofcavitation can be expected.

More specifically, various structures such as a gear pump, a vane pump,and a piston pump can be considered as the oil pump, but, the oil pumpmay be an internal gear pump, for example. That is, the above oil pumpmay further include a drive rotor as an external gear rotated by theinput shaft, and a driven rotor as an internal gear meshing with thedrive rotor so as to be rotated accordingly. The housing may include acontrol hydraulic chamber. The capacity adjustment member may have anannular holding portion configured to rotatably hold the driven rotorfrom an outer periphery of the driven rotor. The capacity adjustmentmember may be configured to be displaced by a hydraulic pressure of thecontrol hydraulic chamber. The capacity-variable mechanism may beconfigured to change relative positions of the drive rotor and thedriven rotor to the inlet port and the discharge port, along with thedisplacement of the capacity adjustment member, such that a dischargeamount of the oil pump is changed.

In a case of the above configuration, at the time of the operation ofthe capacity-variable mechanism, it is necessary to displace the drivenrotor for force-feeding the oil while rotating, and the capacityadjustment member for holding the driven rotor, so that a large force isrequired. In view of this, the aforementioned configuration that canreduce a resistance at the time when the capacity adjustment member isdisplaced is effective.

According to the above variable-capacity oil pump, the communicatingpassage is provided so as to communicate two spaces separated by theguide pin in the guide slot in a case where the displacement of thecapacity adjustment member is regulated by the guide pin inserted intothe guide slot. Hereby, along with the relative displacement of theguide pin in the guide slot, the oil flows through the communicatingpassage as well as the gap between the guide pin and the guide slot.Consequently, the flow resistance of the oil going back and forthbetween two spaces is reduced. This accordingly speeds up the operationof the capacity-variable mechanism, thereby making it possible toimprove response of the control on the pump capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the invention will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a view illustrating a structure of an oil pump according to anembodiment of the present invention, and illustrates a state where apump capacity is maximum;

FIG. 2 is a view corresponding to FIG. 1 and illustrates a state where acapacity of the oil pump is small;

FIG. 3A is an explanatory view schematically illustrating a guide slotand a guide pin of an adjustment ring, according to a first example;

FIG. 3B is a perspective view of the guide pin according to the firstexample which guide pin is provided with a reduced diameter portion;

FIGS. 4A, 4B are views corresponding to FIGS. 3A, 3B according to asecond example in which a groove is provided on an outer peripheralsurface of a guide pin;

FIGS. 5A, 5B are views corresponding to FIGS. 3A, 3B according to athird example in which a tapered part is provided in an tip side of aguide pin;

FIGS. 6A, 6B are views corresponding to FIGS. 3A, 3B according to afourth example in which a through hole is provided in a guide pin;

FIG. 7 is a view corresponding to FIG. 3A according to a fifth examplein which a groove is provided on an inner peripheral surface of a guideslot; and

FIG. 8 is a view corresponding to FIG. 7 according to a sixth example inwhich a communicating passage is provided inside an adjustment ring.

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention is described below with referenceto the accompanying drawings. The present embodiment deals with a casewhere the present invention is applied to an oil supply system of anengine to be provided in an automobile, for example. However, thepresent embodiment is not limited to this. The description of thepresent embodiment is just an example, and a configuration, a purpose,and the like of the present invention are not limited in particular.

The following describes a general configuration of an oil pump 1 withreference to FIGS. 1 and 2. As illustrated in these figures, the oilpump 1 is an internal gear pump including a drive rotor 3 as an externalgear rotated by an input shaft 2, and a driven rotor 4 as an internalgear meshing with this so as to rotate accordingly. An outer peripheryof the driven rotor 4 is held by an adjustment ring 5. As will bedescribed later, the adjustment ring 5 functions as a capacityadjustment member configured to change a pump capacity by displacing thedrive rotor 3 and the driven rotor 4.

A housing 10 of the oil pump 1 is a basin-shaped casting, for example.When viewed from a front side of the engine as illustrated in FIGS. 1,2, the housing 10 has a generally rectangular shape elongated in anup-down direction as a whole. A peripheral wall 11 is formed to surrounda whole circumference of the housing 10. From a different viewpoint, arecessed portion 12 surrounded by the peripheral wall 11 opened towardthe front side of the engine (a near side in the figures) is formedgenerally over the whole housing 10.

When the recessed portion 12 is closed by a cover (not shown)superimposed on the housing 10 from the front side, the recessed portion12 as a receptacle recessed portion (hereinafter, also referred as areceptacle recessed portion 12) configured to receive the drive rotor 3,the driven rotor 4, the adjustment ring 5, and the like is formed. Abottom of the receptacle recessed portion 12 has a through hole (notshown in the figures) having a circular section and formed in a partslightly on an upper side in FIGS. 1, 2 relative to a central part ofthe bottom, and the input shaft 2 is passed through the through hole.

Although not illustrated herein, a pump sprocket is attached to one endof the input shaft 2, so that the pump sprocket is driven by a chain. Inthe meantime, the drive rotor 3 is attached to the other end of theinput shaft 2 by splines (not shown), for example. An outer periphery ofthe drive rotor 3 is provided with a plurality of external teeth 3 a(eleven external teeth 3 a in the example in the figures) having atrochoid curved line or a curved line (e.g., involute, cycloid, or thelike) similar to the trochoid curved line.

In the meantime, the driven rotor 4 is formed in a ring shape, and aninner periphery thereof is provided with a plurality of internal teeth 4a meshing with the external teeth 3 a of the drive rotor 3. The numberof internal teeth 4 a is larger by one (i.e., twelve teeth in theexample in the figures) than the number of external teeth 3 a of thedrive rotor 3. A center of the driven rotor 4 is eccentric relative to acenter of the drive rotor 3 by a predetermined amount, and the externalteeth 3 a of the drive rotor 3 mesh with the internal teeth 4 a of thedriven rotor 4 on a side where the center of the driven rotor 4 iseccentric (on an upper right side in FIG. 1).

The outer periphery of the driven rotor 4 is slidably held by aring-shaped body portion 50 (a holding portion) of the adjustment ring5. Thus, a trochoid pump having eleven blades and twelve nodes isconstituted by the drive rotor 3 and the driven rotor 4 held as such, inthe present embodiment. That is, as illustrated in FIGS. 1, 2, aplurality of chambers R is formed so as to be aligned in acircumferential direction in an annular space between two rotors 3, 4.Volumes of these chambers R increase and decrease while the chambers Rmove in the circumferential direction along with rotation of the tworotors 3, 4.

More specifically, in a range (a range on the right side in FIG. 1) overapproximately 180 degrees in a rotor rotation direction (in a clockwisedirection in the figure) indicated by an arrow in FIG. 1 from a position(an upper right position in FIG. 1) where the teeth of the two rotors 3,4 mesh with each other, the volumes of the chambers R gradually increasealong with the rotation of the two rotors 3, 4. Meanwhile, in aremaining range (a range on the left side in FIG. 1) over approximately180 degrees, the volumes of the chambers R gradually decrease along withthe rotation of the two rotors 3, 4.

The range in which the volumes of the chambers R gradually increasebetween the two rotors 3, 4 is an intake range where oil is taken infrom an inlet port 13. In the meantime, the range where the volumes ofthe chambers R gradually decrease is a discharge range where the oil issent out to a discharge port 14 while the oil is pressurized. That is,as indicated by broken lines in FIGS. 1, 2, the inlet port 13 is formedfor the intake range, and the discharge port 14 is formed for thedischarge range on a bottom face of the receptacle recessed portion 12of the housing 10.

A downstream end 13 a of the inlet port 13 of the present embodiment isformed, for the intake range, in a groove shape in the bottom of thereceptacle recessed portion 12, as described above. The inlet port 13communicates with a port upstream portion 13 c opened on the bottom faceof the receptacle recessed portion 12, via an intermediate groove 13 balso formed in the bottom of the receptacle recessed portion 12.Although not illustrated herein, the port upstream portion 13 c isformed inside the housing 10 and its upstream end is connected to a pipethat is connected to an oil strainer.

As illustrated in FIGS. 1, 2, the intermediate groove 13 b of the inletport 13 faces the after-mentioned guide slot 54. An opening of the portupstream portion 13 c opened on the bottom of the receptacle recessedportion 12 faces a low hydraulic chamber TL (to be described later)formed inside the housing 10 (inside the receptacle recessed portion12). In the meantime, as indicated by broken lines in FIGS. 1, 2, thedischarge port 14 is opened on the bottom of the receptacle recessedportion 12 for the discharge range, and extends inside the housing 10 sothat its upper end communicates with an outlet (not shown) of the oilpump 1.

In the oil pump 1 configured as such, a rotational force of a crankshaftof the engine is transmitted to the pump sprocket via the chain so as todrive the input shaft 2, which causes the drive rotor 3 and the drivenrotor 4 to rotate while meshing with each other, so that the oil istaken into the chambers R formed therebetween from the inlet port 13,and then discharged from the discharge port 14.

Instead of forming the inlet port 13 and the discharge port 14 in thehousing 10 as described above, they may be formed in a coversuperimposed on the housing 10. Either one of the inlet port 13 and thedischarge port 14 may be formed in the housing 10, and the other onethereof may be formed in the cover. The inlet port 13 and the dischargeport 14 may be formed in both the housing 10 and the cover.

The oil pump 1 of the present embodiment includes a capacity-variablemechanism that can change an amount of oil, i.e., a pump capacity, to bedischarged per one rotation of the drive rotor 3 described above. Thecapacity-variable mechanism displaces the adjustment ring 5 by ahydraulic pressure of a control hydraulic chamber TC formed inside thereceptacle recessed portion 12 of the housing 10. Due to thedisplacement of the adjustment ring 5, relative positions of the driverotor 3 and the driven rotor 4 to the inlet port 13 and the dischargeport 14 are changed, so that the pump capacity is changed.

More specifically, the adjustment ring 5 is configured such that thering-shaped body portion 50 configured to hold the driven rotor 4 asdescribed above, first and second overhanging portions 51, 52 eachoverhanging outwardly from an outer periphery of the body portion 50,and an arm portion 53 extending further outwardly from an outerperiphery of the first overhanging portion 51 are formed integrally. Dueto a pressing force of a coiled spring 6 acting on the arm portion 53,the adjustment ring 5 is biased to pivot (displace) around the inputshaft 2 in the clockwise direction in FIG. 1.

A direction where the adjustment ring 5 is displaced is regulated byguide pins 7, 7 provided in a projecting manner on the bottom face ofthe receptacle recessed portion 12 of the housing 10. That is, twooverhanging portions 51, 52 of the adjustment ring 5 have guide slots54, 55 having an elongated-hole-shaped section as illustrated herein,and the guide pins 7 are inserted slidably into the guide slots 54, 55,respectively. Hereby, the displacement of the adjustment ring 5 isregulated to directions where the guide slots 54, 55 extend, that is, tolongitudinal directions of the sections of the guide slots 54, 55. Theguide slots 54, 55 and the guide pins 7 will be described later indetail.

The arm portion 53 of the adjustment ring 5 separates the controlhydraulic chamber TC and the low hydraulic chamber TL from each other,which are formed side by side in the receptacle recessed portion 12 ofthe housing 10. A first sealant 56 is disposed on an outer periphery ofthe arm portion 53, so as to move along with the displacement of theadjustment ring 5 while the first sealant 56 makes sliding contact withthe peripheral wall 11 of the housing 10 to which the first sealant 56is opposed. Due to the first sealant 56, flowing of the oil between thecontrol hydraulic chamber TC and the low hydraulic chamber TL islimited.

In FIG. 1, the low hydraulic chamber TL is disposed in a regionsurrounded by the outer periphery of the adjustment ring 5 and theperipheral wall 11 of the housing 10, from a lower part of thereceptacle recessed portion 12 toward its upper part by detouring arounda right side of the adjustment ring 5. Further, the openings of theintermediate groove 13 b and the port upstream portion 13 c of the inletport 13 are provided so as to face the low hydraulic chamber TL asdescribed above. Accordingly, when the low hydraulic chamber TL receivesa suction pressure of the oil by the rotation of the drive rotor 3 andthe driven rotor 4, its pressure becomes lower than an atmosphericpressure (the pressure reaches a negative pressure).

In the meantime, the control hydraulic chamber TC is formed in a regionwhich is surrounded by the outer periphery of the adjustment ring 5 andthe peripheral wall 11 of the housing 10 and in which flow of the oil islimited by a second sealant 58 provided on the outer periphery of theadjustment ring 5 and the first sealant 56. That is, a protrudingportion 57 is formed on the outer periphery of the adjustment ring 5 soas to project toward an upper left side in FIG. 1, and the secondsealant 58 disposed in the protruding portion 57 moves along with thedisplacement of the adjustment ring 5 while the second sealant 58 makessliding contact with the peripheral wall 11 of the housing 10.

Note that the first and second sealants 56, 58 each have a dimension tothe same degree as a thickness of the adjustment ring 5 (a dimension ina direction perpendicular to a plane of paper of FIGS. 1, 2), and aremade of a resin material and the like excellent in abrasion resistance.

A supply port 15 for a control hydraulic pressure is opened on thebottom face of the receptacle recessed portion 12 so as to face thecontrol hydraulic chamber TC, so that the control hydraulic pressure issupplied from an oil control valve (not shown) via a control oil passage16 as indicated by a virtual line in the figure. A pressing force topivot the adjustment ring 5 counterclockwise in FIGS. 1, 2 is applied tothe arm portion 53 due to the control hydraulic pressure, so that aposition of the adjustment ring 5 is determined so that the pressingforce balances with a pressing force (biasing force) of the coiledspring 6.

The adjustment ring 5 is displaced by adjusting the control hydraulicpressure as such, so that the capacity of the oil pump 1 can be changed.That is, when the control hydraulic pressure is small, the adjustmentring 5 is biased by the pressing force of the coiled spring 6 toward amaximum pump capacity position as illustrated in FIG. 1. When thecontrol hydraulic pressure increases, the adjustment ring 5 thatreceives the control hydraulic pressure pivots (is displaced)counterclockwise in FIGS. 1, 2 against the pressing force of the coiledspring 6, so that the pump capacity is reduced as illustrated in FIG. 2as an example.

In the present embodiment described above, the direction where theadjustment ring 5 is displaced is regulated by the guide slots 54, 55and the guide pins 7. A regulation structure by the guide pin 7 isapproximately the same in two guide slots 54, 55. Accordingly, thefollowing description is made about the guide slot 54 provided in thefirst overhanging portion 51 of the adjustment ring 5.

As schematically illustrated in FIG. 3A, an outer peripheral surface ofthe guide pin 7 having a generally pillar shape serves as a guidesurface that makes sliding contact with an inner peripheral surface (aguided surface) of the guide slot 54. When the adjustment ring 5 isdisplaced so as to change the pump capacity as described above, theinner peripheral surface of the guide slot 54 is guided by the outerperipheral surface of the guide pin 7 along with the displacement.Hereby, the direction where the adjustment ring 5 is displaced isregulated to the longitudinal direction of the section of the guide slot54 (hereinafter just referred to as a “longitudinal direction of theguide slot”).

When the guide slot 54 is displaced in its longitudinal direction from abroken line to a continuous line as illustrated in FIG. 3A along withthe displacement of the adjustment ring 5, for example, the guide pin 7is displaced relative to the guide slot 54. That is, an inner part ofthe guide slot 54 is divided by the guide pin 7 into two spaces A, B onone side and the other side in the longitudinal direction, and the guidepin 7 is relatively displaced inside the guide slot 54 along thelongitudinal direction of the guide slot 54, so that volumes of the twospaces A, B are hereby changed.

For example, when the guide slot 54 is displaced from the broken line tothe continuous line in FIG. 3A and the guide pin 7 is displaced downwardrelative to the guide slot 54, the volume of the space A in the guideslot 54 on the one side (an upper side in the figure) in thelongitudinal direction increases, and the volume of the space B on theother side (a lower side in the figure) in the longitudinal directiondecreases. As a result, as indicated by a continuous-line arrow oil inthe figure, the oil flows from the space B toward the space A (upward inthe figure) in a gap between the outer peripheral surface of the guidepin 7 and the inner peripheral surface of the guide slot 54 that makessliding contact with the outer peripheral surface of the guide pin 7.

In order to regulate the direction of the displacement of the adjustmentring 5 with accuracy, it is necessary to sufficiently narrow the gapbetween the outer peripheral surface of the guide pin 7 and the innerperipheral surface of the guide slot 54 that makes sliding contacttherewith. When the gap between the outer peripheral surface of theguide pin 7 and the inner peripheral surface of the guide slot 54 isnarrow, a flow resistance of the oil flowing through the gap increases,which also increases a resistance to the operation of the adjustmentring 5. When a viscosity of the oil is high like a case where atemperature is low, the resistance increases as compared with a casewhere the temperature is normal or high, which may delay thedisplacement of the adjustment ring 5, so that response of a control onthe pump capacity may decrease.

In contrast, in the present embodiment, at least one of the guide pin 7and the adjustment ring 5 is provided with a communicating passage sothat the two spaces A, B separated by the guide pin 7 inside the guideslot 54 as described above communicate with each other.

First Example of Communicating Passage

More specifically, as indicated by a broken line 7 a in FIG. 3A and asillustrated in a perspective view of the guide pin 7 in FIG. 3B, areduced diameter part 7 a (a small sectional area part having asectional area smaller than that of the other part) is provided in anaxially intermediate part (partially) of the guide pin 7 in the firstexample. The guide pin 7 is provided separately from the housing 10, andthe reduced diameter part 7 a may be formed integrally in amanufacturing process of the guide pin 7, or may be formed by machining.

A recess 70 (a reference sign is shown only in FIG. 3B) formed on theouter periphery of the guide pin 7 at the reduced diameter part 7 a thusprovided serves as a communicating passage. When the guide pin 7 isrelatively displaced in the guide slot 54 along with the displacement ofthe adjustment ring 5 as described above, the oil flows through thecommunicating passage (the recess 70) as indicated by the broken-linearrow in FIG. 3A so that the oil goes back and forth between the twospaces A, B. Therefore, in comparison with a case where the oil flowsonly through the gap between the outer peripheral surface of the guidepin 7 and the inner peripheral surface of the guide slot 54, the flowresistance of the oil can be reduced.

In an example illustrated in FIGS. 3A, 3B, the reduced diameter part 7 ais set to a range at an axially central part of the guide pin 7, withabout one-third of an axial length of the guide pin 7, and the outerperipheral surface of that part of the guide pin 7 which is within arange of about one-third of the guide pin 7 at either end in the axialdirection functions as a guide surface. This makes it possible toachieve stabilization of a function to guide the inner peripheralsurface (the guided surface) of the guide slot 54 by the guide surfaceson both ends of the guide pin 7, that is, the direction where theadjustment ring 5 is displaced.

A sectional area of the communicating passage (the recess 70) may be setto be larger than a sectional area (an area of a range C, illustrated inan exaggerated manner, between the guide surface and the guided surfaceindicated by virtual lines in FIG. 3B) of the gap between the guidesurface on the outer periphery of the guide pin 7 and the guided surfaceon the inner periphery of the guide slot 54 that makes sliding contacttherewith. This makes it possible to increase an effect to reduce theflow resistance of the oil going back and forth between the two spacesA, B in the guide slot 54.

In the variable-capacity oil pump 1 according to the present embodimentdescribed above, by displacing the adjustment ring 5 received in thehousing 10, it is possible to change the pump capacity. At this time,the direction where the adjustment ring 5 is displaced is regulated tothe longitudinal direction of the guide slot 54, 55 by the guide pin 7inserted into the guide slot 54, 55 formed in the adjustment ring 5.

When the adjustment ring 5 is displaced along the longitudinal directionof the guide slot 54, 55 as such, the guide pin 7 is relativelydisplaced inside the guide slot 54, 55 along the longitudinal directionthereof. At this time, the oil flows through the gap between the outerperipheral surface of the guide pin 7 and the inner peripheral surfaceof the guide slot 54, 55 that makes contact therewith, so as to go backand forth between the two spaces A, B in the guide slot 54, 55, and theoil also flows through the communicating passage (the recess 70) formedon the outer periphery of the guide pin 7.

Because of this, even if the gap between the outer peripheral surface ofthe guide pin 7 and the inner peripheral surface of the guide slot 54,55 is narrowed sufficiently so as to regulate the direction of thedisplacement of the adjustment ring 5 with accuracy, the flow resistanceof the oil flowing through not only the gap but also the communicatingpassage (the recess 70) can be reduced sufficiently. This allows theadjustment ring 5 to be displaced fast, thereby making it possible toincrease response of a control on the pump capacity. This is effectiveparticularly at the time when the viscosity of the oil is high like acase where the temperature is low.

Second Example

FIGS. 4A, 4B illustrate a second example in which a pair of grooves 71,71 is formed on an outer periphery of an axially intermediate part(partially) of a guide pin 7 at a generally semicircular interval, sothat the intermediate part is provided as a small sectional area parthaving a sectional area smaller than that of the other part. The pair ofgrooves 71, 71 may be also formed integrally in a manufacturing processof the guide pin 7, or may be machined. Further, it is preferable that asectional area of each of the grooves 71 be set to be larger than asectional area of a gap between a guide surface on an outer periphery ofthe guide pin 7 and a guided surface on an inner periphery of a guideslot 54.

The guide pin 7 thus provided with the grooves 71 is attached to ahousing 10 so that orientations in which the grooves 71 extend are alonga longitudinal direction of the guide slot 54, 55. Hereby, the grooves71 each serve as a communicating passage that communicates two spaces A,B in the guide slot 54 with each other. When the guide pin 7 isrelatively displaced in the guide slot 54 along with displacement of anadjustment ring 5, oil flows through the communicating passage (thegroove 71) so that the oil goes back and forth between the two spaces A,B.

In a case where the pair of grooves 71, 71 are provided like thisexample, rigidity and strength of the guide pin 7 can be easilyincreased as compared with a case where the reduced diameter part 7 a isprovided like the first example. However, it is necessary to attach theguide pin 7 to the housing 10 with the directions of the grooves 71, 71being along the longitudinal direction of the guide slot 54, 55.Further, even in the second example, outer peripheral surfaces of bothaxial ends of the guide pin 7 except the grooves 71, 71 make slidingcontact with an inner peripheral surface (a guided surface) of the guideslot 54, which achieves stabilization of a guiding function.

Third Example

FIGS. 5A, 5B illustrate a third example in which a tip end side (anupper side in FIG. 5B) of a guide pin 7 is provided as a small sectionalarea part and as a tapered part 7 b (a sectional-area gradually changingpart), so that a space 72 around the tapered part 7 b serves as acommunicating passage. The tapered part 7 b may be also formedintegrally in a manufacturing process of the guide pin 7 or may bemachined. Alternatively, the guide pin 7 itself may be formed integrallywith a bottom of a receptacle recessed portion 12 of a housing 10 at thetime of casting the housing 10. In this case, since the tip end side ofthe guide pin 7 is the tapered part 7 b, demolding is performed easily.

In this example, similarly to the first example, the space 72 (areference sign is shown only in FIG. 5B) around the tapered part 7 b(the small sectional area part) of the guide pin 7 serves as thecommunicating passage, so that oil flows therethrough, which makes itpossible to reduce a flow resistance thereof. On the other hand, outerperipheral surfaces of a base end and an intermediate part of the guidepin 7 except the tapered part 7 b serve as a guide surface that makessliding contact with an inner peripheral surface (a guided surface) of aguide slot 54, so that a guiding function can be secured.

Note that a size of the tapered part 7 b may be set such that a passagesectional area of the oil flowing through the space 72 around thetapered part 7 b is larger than a sectional area of a gap between aguide surface on an outer periphery of the guide pin 7 and a guidedsurface on an inner periphery of a guide slot 54.

Fourth Example

FIGS. 6A, 6B illustrate a fourth example in which a communicatingpassage (a through hole 73) is provided so as to penetrate through aguide pin 7. The through hole 73 may be also formed integrally in amanufacturing process of the guide pin 7 or may be machined. Even inthis example, oil flows through the communicating passage (the throughhole 73), so that a flow resistance thereof can be reduced.

In the fourth example, a whole outer peripheral surface of the guide pin7 serves as a guide surface and makes sliding contact with an innerperipheral surface (a guided surface) of a guide slot 54, so that aguiding function is easy to be secured. However, similarly to the secondexample, it is necessary for the guide pin 7 to be attached to a housing10 so that an orientation in which the through hole 73 extends is alonga longitudinal direction of the guide slot 54, 55. Note that it ispreferable that a sectional area of the through hole 73 be set to belarger than a sectional area of a gap between a guide surface on anouter periphery of the guide pin 7 and a guided surface on an innerperiphery of the guide slot 54.

Fifth Example

FIG. 7 illustrates a fifth example in which a communicating passage isnot provided in a guide pin 7, but is provided as a groove 54 a openedon an inner peripheral surface of a guide slot 54 with which an outerperipheral surface of the guide pin 7 makes sliding contact. The groove54 a may be molded integrally with the guide slot 54 in a manufacturingprocess of a housing 10, or may be machined after the guide slot 54 ismolded.

As illustrated herein, the groove 54 a extends in a longitudinaldirection of the guide slot 54, and one end (an upper end in FIG. 7)thereof is placed at an end part (an upper end in FIG. 7) on one side ofthe guide slot 54 in the longitudinal direction. Even when the guide pin7 is placed closest to the one side (an upper side in FIG. 7) in thelongitudinal direction of the guide slot 54, the groove 54 a faces aspace A on the one side. In the meantime, the other end (a lower end inFIG. 7) of the groove 54 a is placed in the other end (the lower end inFIG. 7) of the guide slot 54 in the longitudinal direction, and evenwhen the guide pin 7 is placed closest to the other side (a lower sidein FIG. 7) of the guide slot 54 in the longitudinal direction, thegroove 54 a faces a space B on the other side.

When the guide pin 7 is relatively displaced in the guide slot 54, thegroove 54 a formed as such functions as a communicating passage thatcommunicates two spaces A, B in the guide slot 54 without depending on aposition of the guide pin 7, so as to allow oil to flow through thecommunicating passage (the groove 54 a) along with relative displacementof the guide pin 7, so that the oil goes back and forth between the twospaces A, B. Note that it is preferable that a sectional area of thegroove 54 a be set to be larger than a sectional area of a gap between aguide surface on an outer periphery of the guide pin 7 and a guidedsurface on an inner periphery of the guide slot 54.

Sixth Example

FIG. 8 illustrates a sixth example in which both ends of a communicatingpassage 59 formed inside an adjustment ring 5 are opened on an innerperipheral surface of a guide slot 54. The communicating passage 59 canbe formed by boring by means of a drill or the like, for example, afterthe guide slot 54 is molded in a manufacturing process of a housing 10.

As illustrated herein, the communicating passage 59 extends in alongitudinal direction of the guide slot 54, and one end (an end part ona upper side in FIG. 8) of the communicating passage 59 is opened in anend part (an upper end in FIG. 8) of the guide slot 54 on one side inthe longitudinal direction, so as to face a space A. Further, the otherend (an end part on a lower side in FIG. 8) of the communicating passage59 is opened in an end part (a lower end in FIG. 8) of the guide slot 54on the other side in the longitudinal direction, so as to face a spaceB. Note that it is preferable that a sectional area of the communicatingpassage 59 be set to be larger than a sectional area of a gap between aguide surface on an outer periphery of the guide pin 7 and a guidedsurface on an inner periphery of the guide slot 54.

When the guide pin 7 is relatively displaced in the guide slot 54, thecommunicating passage 59 formed as such communicates two spaces A, Bwith each other without depending on a position of the guide pin 7, thatis, even if the guide pin 7 is placed closest to the one side (the upperside in FIG. 8) in the longitudinal direction of the guide slot 54 oreven if the guide pin 7 is placed closest to the other side (the lowerside in FIG. 8). This allows oil to flow through the communicatingpassage 59 along with the relative displacement of the guide pin 7, sothat the oil goes back and forth between the two spaces A, B.

The embodiment described above deals with a case where the presentinvention is applied to the oil pump 1 of an automotive engine. However,the present invention is not limited to this, and the present inventioncan be applied to an oil pump for an engine to be provided in othervehicles except the automobile. The number of cylinders of the engineand a type (a V type, a horizontal opposed type, and the like) of theengine are not limited in particular, and a type of fuel (gasoline,diesel oil, fuel gas, and the like) is also not limited in particular.Further, the present invention can be applied to an oil pump of atransmission.

Examples of the communicating passage to be provided in the guide pin 7or the guide slot 54, 55 are described as the first to sixth examples.However, these are just examples and do not limit the configuration ofthe present invention. That is, for example, not one but a plurality ofreduced diameter parts 7 a in the first example may be provided, or notone but a plurality of through holes 73 in the fourth example may beprovided. Further, only one groove 71 in the second example may beprovided. Further, two or more grooves 54 a in the fifth example or twoor more communicating passages 59 in the sixth example may be provided.

Further, positions to provide the reduced diameter part 7 a, the grooves71, 71 the through hole 73, the groove 54 a, the communicating passage59, and the like are also not limited to the first to sixth examples,and the reduced diameter part 7 a, the grooves 71, 71, the through hole73, the groove 54 a, the communicating passage 59, and the like may beprovided in combination appropriately.

Furthermore, a general structure of the oil pump 1 described in theabove embodiment is just an example. For example, instead of using thecoiled spring 6 to bias the adjustment ring 5, various elastic memberssuch as a leaf spring can be used. Further, the oil pump is not limitedto an inner oil pump, and the present invention is applicable to variousvariable-capacity oil pumps such as a vane pump or a piston pump, forexample.

The above embodiment can increase response to change a pump capacity ina variable-capacity oil pump to be provided in an engine or the like.Accordingly, the above embodiment yields a high effect when the aboveembodiment is applied to an engine of an automobile in which a drivingstate is changed largely.

What is claimed is:
 1. An oil pump comprising: an input shaft; an inletport; a discharge port; a capacity-variable mechanism configured tochange a discharge amount per one rotation of the input shaft, thecapacity-variable mechanism including a capacity adjustment member, thecapacity adjustment member having a guide slot having an elongated-holeshape, the guide slot including a guided surface provided on an innerperiphery of the guide slot; and a housing including a guide pin, theguide pin being inserted into the guide slot, the guide pin including aguide surface provided on an outer periphery of the guide pin, the guidepin being configured to regulate displacement of the capacity adjustmentmember to a longitudinal direction of the guide slot, the guide pinbeing configured to separate the guide slot into a first space and asecond space in the longitudinal direction, the guide surface of theguide pin making sliding contact with the guided surface of the guideslot, oil flowing between the first space and the second space via a gapbetween the guide surface and the guided surface, and at least one ofthe guide pin and the capacity adjustment member being provided with acommunicating passage, the communicating passage being configured tocommunicate the first space with the second space.
 2. The oil pumpaccording claim 1, wherein a sectional area of the communicating passageis larger than a sectional area of the gap between the guide surface andthe guided surface.
 3. The oil pump according to claim 1, wherein theguide pin includes a first sectional area part and a second sectionalarea part along an axial direction of the guide pin, the first sectionalarea part having a sectional area smaller than a sectional area of thesecond sectional area part, and the guide pin includes a recess providedon an outer peripheral surface of the guide pin in the first sectionalarea part, the recess constituting the communicating passage.
 4. The oilpump according to claim 3, wherein the first sectional area part isprovided at an axially intermediate part of the guide pin.
 5. The oilpump according to claim 3, wherein the first sectional area part of theguide pin includes a tapered part having a sectional area that graduallyincreases toward the second sectional area part.
 6. The oil pumpaccording to claim 1, wherein the communicating passage penetratesthrough the guide pin, and the communicating passage is configured tocommunicate the first space with the second space.
 7. The oil pumpaccording to claim 1, wherein an inner peripheral surface of the guideslot has a groove extending in the longitudinal direction of the guideslot, and the groove constitutes the communicating passage.
 8. The oilpump according to claim 1, wherein the communicating passage is providedinside the capacity adjustment member, and both ends of thecommunicating passage are opened on an inner peripheral surface of theguide slot.
 9. The oil pump according to claim 1, wherein the housingincludes a low hydraulic chamber, and the guide slot communicates withthe inlet port via the low hydraulic chamber.
 10. The oil pump accordingto claim 1, further comprising: a drive rotor as an external gearrotated by the input shaft; and a driven rotor as an internal gearmeshing with the drive rotor so as to be rotated accordingly, whereinthe housing includes a control hydraulic chamber, the capacityadjustment member has an annular holding portion configured to rotatablyhold the driven rotor from an outer periphery of the driven rotor, thecapacity adjustment member is configured to be displaced by a hydraulicpressure of the control hydraulic chamber, and the capacity-variablemechanism is configured to change relative positions of the drive rotorand the driven rotor to the inlet port and the discharge port, alongwith the displacement of the capacity adjustment member, such that adischarge amount of the oil pump is changed.